A vaginal fibroleiomyoma in a ten-year-old spayed pug dog - a case report

A ten-year-old pug, spayed two years before, was presented for a bleeding vaginal mass. The owner reported tenesmus, dysuria progressing to anuria and a mass protruding intermittently from the vulva. There was no report of signs of heat after ovariectomy or exogenous estrogen administration. Antimüllerian hormone and progesterone were 0.01 and 0.1ng/ml respectively. Vaginal examination revealed a single, painful mass with areas of calcification and necrosis, measuring 5x5 cm, involving the dorsal wall of the caudal vagina. Vaginal cytology showed no sign of estrogen impregnation. No ovarian tissue was identified at abdominal ultrasound. The mass was resected through an episiotomy and a partial thickness incision was made around the pedicle. Because of diffuse bleeding, hemostasis was controlled with vaginal mesh left in situ during 48h. Histology revealed a fibroleiomyoma with some atypical areas with anysocaryosis. Estrogen receptors alpha ER 1D5 were found by immunohistochemistry in the tumor, including atypical areas, healthy vaginal epithelium and smooth muscles. Half of the benign vaginal tumors have estrogen receptors. In this case, there is no current evidence of residual ovarian syndrome. The first hypothesis is that the vaginal mass was already present at the time of ovariectomy. Therefore vaginal examination before late neutering should be recommended. The second hypothesis is that the mass appeared and grew after sterilisation without estrogen stimulation, even if estrogen receptors were present. In fact, these were found in healthy vaginal tissue. It is suspected that they persist without estrogen stimulation. Contrary to mammary tumors, malignancy of vaginal tumors can not be predicted in spayed bitches.